Security Digest · Vulnerability record · Known exploited
CVE-2023-6549: Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability
Exploited in the wild (CISA KEV). Improper Restriction of Operations within the Bounds of a Memory Buffer in NetScaler ADC and NetScaler Gateway allows Unauthenticated Denial of Service and Out-Of-Bounds Memory Read
CISA KEV · added 2024-01-17 CVSS 8.2 High EPSS 57.6% · p99
Should you act?
Exploited: patch now if you run it
CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Yes, if you run Citrix NetScaler ADC and NetScaler Gateway. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2024-01-17, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2024-02-07; treat that as the outer limit, not the target.
- EPSS 57.6%, percentile 99: FIRST’s model estimates a 57.6% chance of exploitation activity in the next 30 days, higher than 99% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
What it is
Improper Restriction of Operations within the Bounds of a Memory Buffer in NetScaler ADC and NetScaler Gateway allows Unauthenticated Denial of Service and Out-Of-Bounds Memory Read
CISA’s summary
Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow vulnerability that allows for a denial-of-service when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.
Weakness type: CWE-119.
Product: Citrix NetScaler ADC and NetScaler Gateway · Assigned by: Citrix · Published: 2024-01-17
Affected and fixed versions
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| Cloud Software Group | NetScaler ADC | 14.1 < 12.35, 13.1 < 51.15, 13.0 < 92.21, 13.1-FIPS < 37.176, 12.1-FIPS < 55.302, 12.1-NDcPP < 55.302 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| Citrix | 3.1 | 8.2 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: added 2024-01-17; federal due date 2024-02-07. Known ransomware use: Unknown.
- CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- CISA SSVC assessment: exploitation active, automatable yes, technical impact partial.
- FIRST EPSS (model of 2026-10-21): 57.63% probability of exploitation activity in the next 30 days; percentile 99.
Timeline
- — Added to CISA’s Known Exploited Vulnerabilities catalog
- — CVE record published by Citrix
- — CISA remediation deadline for US federal agencies
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- Listed in CISA KEV notes (support.citrix.com) support.citrix.com
Vulnerability records
- CVE.org record CVE-2023-6549 cve.org
- NVD entry CVE-2023-6549 nvd.nist.gov
Government
All exploited Citrix vulnerabilities · Today’s Security Digest